1. Field of the Invention
This invention relates to closures for containers which provide a visual indication of attempts to open or otherwise tamper with the closure and more particularly to such a closure with a tear out tab which can be molded integrally with the closure in a straight draw mold without the need for slides or cams and which does not require modification to threaded containers with the typical transfer bead.
2. Background Information
There is a great deal of demand today for container closures which provide a visual indication that a container has been previously opened or tampered with in order to assure a user of the integrity of the contents of the container. Numerous designs have been proposed for such closures, many of which are difficult, and therefore expensive, to mold. In addition, some such closures require assembly of separate parts and some require a customized finish on the container.
It is common for containers to have a flange projecting radially from a threaded neck. This flange is engaged by equipment which transports the container during processing and therefore is referred to as a transfer bead. Many tamper evident closures include an annular tamper band attached to a closure skirt by frangible bridges circumferentially spaced around the tamper band and have a radially inwardly directed flange which engages the transfer bead on the container as the closure is threaded onto the container. When the closure is unscrewed, the inwardly directed flange remains engaged by the transfer bead. Axial displacement of the closure produced by rotation of the helical threads generates a force which fractures the bridges to separate the tamper band from the closure skirt, thereby providing a visual indication that the container has been opened or tampered with. Typically, such closures require slides or cams in the molds that produce them to form the bridges and the radially inwardly directed flange. This adds to the cost of making such closures and slows down production.
U.S. Pat. No. 4,372,456 discloses a container closure having such a tamper band connected to the closure skirt by a number of frangible bridges. A trapezoidal tab connected to the tamper band by additional frangible bridges extends into an axially extending slot in the bottom of the closure skirt, but is not connected to the closure skirt. When the cap is unscrewed, it separates axially from the tamper band which is engaged by the transfer bead on the container. While the tab is not directly connected to the closure skirt, the trapezoidal shape of the tab and slot create an interference fit as the closure is unscrewed which results in fracturing of the bridges and separation of the tab from the tamper band. The void left by removal of the tab provides a visual indication of tampering or prior removal of the closure. Such a closure; however, requires a mold with slides in order to form the bridges, tab and slot.
It is an object of the present invention to provide a container closure which has a removable tab for providing a visual indication of tampering, but which can be molded with a straight draw mold without the need for slides.
It is also an object of the invention to provide such a closure which can be used on containers with a conventional transfer bead without need for modification to the container.